The Mosquitoes: Over 70 species
of mosquitoes have been found in Florida, and more than 40 species have
been identified in Pasco County. Each mosquito species has a different
habitat, behavior and preferred source of blood. Organized mosquito control
is necessary because mosquitoes are not only a nuisance as biting insects,
but are also involved periodically in transmitting diseases to humans
and animals.

Mosquitoes Need Water: All mosquitoes have four stages
of development - egg, larva, pupa, and adult - and spend their larval
and pupal stages in water.

While some mosquitoes lay their eggs on the surface
of the water, the most abundant species deposit their eggs on moist soil.
These eggs may lie dormant for several months and even years and will
not hatch until they are covered by rain water or tides. Four to five
days after the eggs hatch, the larvae are full grown. By this time, they
have changed their shape - become less active - and are known as pupae.
After one to two days, the pupal skin splits at the water's surface, and
the adults emerge and are soon ready to bite.

Only the Females Bite: When an adult mosquito emerges
from the pupa, they mate, and the female seeks a blood meal to obtain
the protein necessary for the development of her eggs. With one blood
meal, a female may produce as many as 250 or more eggs. After a blood
meal, it takes 3-5 days for blood to be digested and the eggs to develop.

The male mosquito does not take a blood meal, but
may feed on plant nectar. He lives for only a short time after mating,
while the female can live for over two weeks, producing 2-4 egg batches.
Females transmit diseases when they live long enough to spread viruses,
microfilaria, etc. from the first blood meal victim to the second blood
meal victim. Only a very small percentage of mosquitoes live this long.

Culex larvae (wigglers) develop as four instars
in 5-10 days, and then they become pupae (tumblers).

Culex pupae metamorphose over 1-2 summer days
into adults. They do not eat during this period.

Females seek a place to lay their eggs, and the site
chosen is probably based on clues from chemical receptors on their body.
Mosquitoes have two general egg laying (oviposition) strategies which
are usually specific for each species. Mosquitoes will either lay eggs
on existing water bodies, or they will lay eggs at sites that will later
be flooded. In either case, the egg requires 1-2 days of water before
the 1st instar larvae are released. The female mosquito stores the sperm
she received through mating, and eggs are fertilized at the time they
are laid. The development time of the egg is about 1-2 days, and during
this period the egg turns from white to black as its outer shell hardens
to protect it from a hostile environment. Some eggs may hatch several
months and even years after they are laid if they are not exposed to water
during that time.

Once the eggs hatch, the larvae begin eating voraciously, and they grow
rapidly, from about 1/16-inch to nearly 3/8-inch or greater in size. Mosquito
larvae eat microscopic plants (algae) and animals (phytoplankton) by filter
feeding and grazing. Mosquitoes (and other invertebrates) do not have
an internal skeleton like we do to support their organ systems. Instead,
they have a hard external skeleton (exoskeleton) made of chitin. This
hard exoskeleton hinders their rapid growth, and they shed it four times
during the larval stage. Each one of the sub-stages in mosquito larval
development is called an "instar". This development process
usually takes about 4-10 days in summer months, depending on the species
and ambient temperature. However, some mosquitoes spend the winter in
the water as 3rd instar larvae, and hatch off together in great hordes
in spring as water temperatures rise. Those mosquito species that lay
their eggs in areas that later are flooded with tides or rainwater also
tend to have vast synchronous broods, whose peak population numbers are
low during subsequent development times. In contrast, those species that
lay their eggs on the water surface tend to have a more constant population
numbers (usually too many for our comfort) if the environmental conditions
are stable.

The next stage is the pupa, or tumbler. This stage
usually lasts about 2 days. During this time the mosquito transforms from
the aquatic larva into the flying adult. The pupa does not feed. If you
look carefully at a pupa through its semi-transparent exoskeleton, you
will see the developing adult inside. After a suitable development time,
the adult emerges from the exoskeleton at the water surface, dries its
wings, and takes flight to begin the cycle again.

The mosquito must breathe air to live. In both the
larval and the pupal stage, the mosquito takes advantage of the surface
tension of the water to stay attached to the surface layer so that they
may gather air through special appendages called "siphons" for
larvae and "horns" for pupae. Adults also use the water surface
tension to stay suspended when they are emerging from pupal cases, drying
their wings, and/or landing and laying their eggs.